<!DOCTYPE html>
<html lang="en"><head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
    .box{
        width: 80%;
        height: 400px;
        background-color: tomato;
        margin:auto;
    }
    </style>
</head>
<body>
    <div class="box">
        <div class="top"></div>
    </div> 

</body></html>